Housing
What size is your tank? 5.5 Gallons
What temperature is your tank? 80F
Does your tank have a filter? Yes
Does your tank have an air stone or other type of aeration? No
Is your tank heated? Yes
What tank mates does your betta fish live with? None

Food
What type of food do you feed your betta fish? Omega One Betta Pellets
How often do you feed your betta fish? One pellet twice a day to try to keep bloating from coming back and fasting once a week if it doesn't.
Maintenance
How often do you perform a water change? Once a week
What percentage of the water do you change when you perform a water change? 50%
What type of additives do you add to the water when you perform a water change? Seachem Prime and Stress Coat

Water Parameters:
Have you tested your water? If so, what are the following parameters?

Ammonia: 0
Nitrite: 0
Nitrate: 5
pH: 8.2

Symptoms and Treatment
How has your betta fish's appearance changed? Sometimes a bit bloated.
How has your betta fish's behavior changed? Trouble swimming and getting air.
When did you start noticing the symptoms? 2 months ago
Have you started treating your fish? If so, how? First with fasting, then with epsom salt, then with API General Cure, then with Tetracycline over the past two months with plenty of time in between different treatments. Did better with the Tetracylcline but is now back to having issues.
Does your fish have any history of being ill? Ick when I first got him, but otherwise just this.
How old is your fish (approximately)? Um... Estimate 6 months to a year. Had him for a few months and he was full grown when I got him.

I am at my wits end with this SBD. He's back in a big net to keep him from struggling so hard to get air. Nothing seemed to help until the Tetracycline but even that didn't have him back to normal, maybe at 80% better. I put him back in his normal tank on Tuesday and he's been the same until I came home Saturday night from work and he was struggling to get air again so he's back in the net.

If he's having trouble swimming and getting air, you have a few other options besides the net (the net might be very stressful for him - which won't help his SBD any, and he could get his fins tangled up in it and tear them) to help him. You can lower the water level in your tank so he doesn't have to swim so far - if your heater is completely submersible, this is a good option. You can fill a small container with just a little bit of water and float him in it in the tank. Or, if you have one, you can put him in a small, heated hospital tank with just a little water.
As I mentioned before, I feel these are better alternatives to the net. If he gets tangled on the net, he may have difficulty getting air as well.
My guy struggles from SBD and constipation quite often, and this last round, I've tried the Epsom salts, and he's still not improving, so if anyone with more knowledge has any suggestions for the OP, I would love to hear them as well.